An aqueous electrolyte solution, a power storage device filled with the aqueous electrolyte solution, and a manufacturing method of the power storage device are illustrated. The aqueous electrolyte solution comprises alkali metal cations of different types. With the hydration enthalpy of the alkali metal cations of the different types, a simulated boiling point of the aqueous electrolyte solution is higher than the 105° C. of the conventional aqueous electrolyte solution. After processed by the reflow furnace at 250° C., the power storage device has no cracks found on its appearance, which meets the electrical requirements, and overcomes the problem of bursting of the power storage device filled with conventional aqueous electrolyte solution. The housing of the power storage device adopts liquid crystal polymer, and/or the power storage device is firstly vacuumed and then packaged, therefore increasing coulombic efficiency of electrical testing of the power storage device.